In the conventional manufacture of methoxyisopropylamine, methoxyisopropanol is contacted with ammonia in the presence of a catalyst under amination conditions to produce methoxyisopropylamine and byproduct water. One of the problems associated with the recovery of the methoxyisopropylamine from the reaction mixture is that an azeotrope consisting of about 14% water and 86% methoxyisopropylamine is formed. The methoxyisopropylamine-water azeotrope is extremely difficult to separate and therefore produce a methoxyisopropylamine product which is essentially anhydrous. eg., less than about 1% water. Any residual water in the methoxyisopropylamine tends to affect its usefulness as a reactant in many chemical reactions.
The following patents illustrate various approaches to the separation of amine-water azeotropes.
U.S. Pat. No. 4,868,335 discloses the recovery of mono-n-hexylamine from a mono-n-hexylamine-water azeotrope. To effect separation, the azeotrope is contacted with di-n-hexylamine or a mixture of di-n-hexylamine and tri-n-hexylamine. The di-n-hexylamine forms a lower boiling azeotrope with water and is removed by distillation. The organic phase then can be separated from the aqueous phase by decanting.
U.S. Pat. No. 3,433,788 discloses a process for recovering amines from aqueous solutions by solvent treatment and distillation. In particular the invention pertained to processes for the recovery of morpholine from aqueous solutions wherein the N-alkylmorpholines and some other amines form an azeotrope with water which could not be separated. Dewatering techniques involving the addition of sodium hydroxide were suggested, however, it was pointed out that the sodium hydroxide had to be recovered and that large amounts of water had to be removed by distillation. Ethyl ether was disclosed as being an extractant for morpholine but was unsatisfactory because of losses due to the high volatility of ethyl ether. The patentees suggested the utilization of an inert, water-immiscible, selective liquid organic solvent as an extractant. Specifically the extractants listed were organic vehicles which were inert to the amine and had a boiling point higher than the amine compound. Solvents included aliphatic alcohols, saturated aliphatic hydrocarbons, halogenated aliphatic hydrocarbons, saturated ketones, ester derivatives of ethyl and diethyleneglycol, alkylphosphoric acids, alkylcarboxylic acids, and alkylamines.
U.S. Pat. No. 4,407,703 discloses an amine separation process wherein isomers of alkylamines are separated into their constituent components. The process involves first distilling the mixture and recovering at least one pure component. The remainder of the mixture is then subjected to a multi-stage liquid extraction in approximately five theoretical stages using water as an extractant. Ethylamines comprising mono, di- and triethylamines are representative of the alkylamines separated by the process.